Mri safety device means and methods thereof

ABSTRACT

A magnetic shielding mechanism for preventing penetration of metallic objects through an aperture, towards the open bore of an magnetic resonance imaging device, where the magnetic field is maximized. The magnetic resonance imaging device produces a fringing magnetic field that decreases with increasing distance (L) from the aperture. The mechanism includes at least one magnet with a magnetic field. The mechanism is affixed at a distance from the aperture of magnetic resonance imaging device.

FIELD OF THE INVENTION

The present invention pertains to safety during imaging proceduresrelated to magnetic fields and more particularly to protection ofpersonnel and equipment involved in MRI diagnosis.

BACKGROUND OF THE INVENTION

In general, the static magnetic fields in MRI systems may be more thanabout 0.5 T; some such systems have static magnetic fields greater than3 T. These magnetic fields will attract metal objects in the vicinity ofthe static magnets. If the object is in the vicinity of the MRI'sopening, such as an opening to allow entrance of a subject to beanalyzed, the object can become very difficult to remove from theinterior of the MRI. Worse, in an MRI located within the hospital, forimaging patients, such a magnetic fringing field can be physicallydangerous to the patient, if not fatal.

Fringe fields from a high field strength can extend to a distancedetermines roughly by the equation X=αβ₀, where α is a constantdependent on the magnet bore size and magnet configuration. Anunshielded 1.5 T magnet has a 1 mT fringe field at a distance of ^(˜)9.3m, a 0.5 mT field at 11.5 m, and a 0.3 mT field at 14.1 m from thecenter of the magnet. To reduce the extent of the magnetic fringe field,passive (such as thick metal walls close to the magnet) and active(electromagnet systems placed in the magnet housing, superconductivemagnets U.S. Pat. No. 5,883,558, U.S. Pat. No. 5,565,831 magneticshielding are applied. The distance of a shielded fringe fieldsurrounding the MRD opening can be reduced to about 2 meters or less.

Despite the achievable reduction of the magnetic fringe fieldboundaries, the existence of such field provides room for the abovementioned dangers in the MRD vicinity. Therefore, there is a long-feltneed to provide an automatic and safe means of preventing loose metalobjects from entering the fringe field and the MRD bore and protectingthe patients from metallic instruments.

SUMMARY OF THE INVENTION

It is an object of the present invention to disclose a system formagnetic shielding mechanism (MSM) for avoiding penetration of metallicobjects throughout an aperture, towards the open bore of an MRI device(MRD), where the magnetic field (B) is maximized; the MRD producesfringing magnetic field (B_(P/L)) which decreases with increasingdistance (L) from the aperture; the MSM comprising at least one magnetwith a magnetic field B_(MSM); the MSM is affixed at a distance L_(MSM)from the MRD's aperture; wherein at any distance L, B_(MSM)>>B_(F/L).

It is another object of the present invention wherein the MSM as definedin any of the above is configured as a rim, at least partiallyencircling the open bore.

It is another object of the present invention wherein the MSM as definedin any of the above comprises an array of a plurality of magnetsdisposed along at least a part of the circumference of the rim.

It is another object of the present invention wherein the MSM as definedin any of the above is in connection with a horizontal patient bed or agantry (together defined as ‘gantry’) configured to reversiblyreciprocally maneuver into and out of the open bore, along the mainlongitudinal axis of the same, wherein the MSM is adapted to one of agroup consisting of (i) encircle at least a portion of the gantry, (ii)located in connection to the gantry, (iii) be comprised within or on topat least a portion of the gantry and a combination thereof.

It is another object of the present invention wherein the MSM as definedin any of the above comprises a plurality of magnets.

It is another object of the present invention wherein the MSM as definedin any of the above comprises a plurality of magnets are provided in anarray.

It is another object of the present invention wherein the MSM as definedin any of the above comprises metallic objects selected from a groupconsisting of medical devices, needles and surgical instruments,laboratory items, dress-ware, garments, and foot-ware, ferrous-basedmaterials, nickel alloys and stainless steel of ferritic and martensiticcrystalline structure and any combination thereof.

It is another object of the present invention wherein the MSM as definedin any of the above comprises communication means thereby providing aremote connection with an MRD.

It is another object of the present invention wherein the MSM as definedin any of the above is in connection with an alarming mechanism incommunication with at least one MSM, and further wherein at least oneMSM is provided in connection to a gate alarming when metallicinstrument penetrate via the gate.

It is another object of the present invention wherein the MSM as definedin any of the above is in connection with an MRD-guard mechanism (GM),the GM is selected from a group consisting of (i) MRD'saperture-blocking mechanism, (ii) magnetic field shutter, (iii) one ormore MSMs, and a combination thereof, wherein the alarming mechanism incommunication with the GM when a metallic instrument penetrate via thegate.

It is another object of the present invention wherein the MSM as definedin any of the above is in communication with a metal detector.

It is another object of the present invention wherein the MSM as definedin any of the above MSM is portable.

It is another object of the present an MRD, comprising one or moremagnetic MSMs for avoiding penetration of metallic objects throughout anaperture, towards the open bore of the MRD where the magnetic field (B)is maximized; the MRD produces fringing magnetic field (B_(P/L)) whichdecreases with increasing distance (L) from the aperture; wherein theMSM comprising at least one magnet with a magnetic field B_(MSM);wherein the MSM is affixed at a distance L_(MSM) from the MRD'saperture; and further wherein at any distance L, B_(MSM)>>B_(F/L).

It is another object of the present invention wherein the MRD as definedin any of the above comprises an MSM which is configured as a rim, atleast partially encircling the open bore.

It is another object of the present invention wherein the MRD comprisesan array of a plurality of magnets disposed along at least a part of thecircumference of the rim.

It is another object of the present invention wherein the MRD as definedin any of the above, the MRD additionally comprises a horizontal patientbed or a gantry configured to reversibly reciprocally maneuver into andout of the open bore, along the main longitudinal axis of the same,wherein the MSM is adapted to one of a group consisting of (i) encircleat least a portion of the gantry, (ii) located in connection to thegantry, (iii) be comprised within or on top at least a portion of thegantry and a combination thereof.

It is another object of the present invention wherein the MRD as definedin any of the above comprises an MSM and the MSM comprises a pluralityof magnets.

It is another object of the present invention wherein the MRD as definedin any of the above comprises an MSM, wherein in the aforesaid MSM, theplurality of magnets is provided in an array.

It is another object of the present invention wherein the MRD as definedin any of the above wherein the metallic objects are selected from agroup consisting of medical devices, needles and surgical instruments,laboratory items, dress-ware, garments, and foot-ware, ferrous-basedmaterials, nickel alloys and stainless steel of ferritic and martensiticcrystalline structure and any combination thereof.

It is another object of the present invention wherein the MRD as definedin any of the above is in a remote connection with an MSM as definedabove.

It is another object of the present invention wherein the MRD as definedin any of the above which comprises an alarming mechanism incommunication with at least one MSM, wherein at least one MSM isprovided in connection to a gate alarming when metallic instrumentpenetrate via the gate.

It is another object of the present invention wherein the MRD as definedin any of the above further comprises an MRD-guard mechanism (GM), theGM is selected from a group consisting of (i) MRD's aperture-blockingmechanism, (ii) magnetic field shutter, (iii) one or more MSMs, and acombination thereof, wherein the alarming mechanism is in communicationwith the GM when a metallic instrument penetrates via the gate.

It is another object of the present invention wherein the MRD as definedin any of the above is in connection with an MSM which is incommunication with a metal detector.

It is another object of the present invention wherein the MRD as definedin any of the above wherein the MSM is portable.

BRIEF DESCRIPTION OF THE FIGURES

In order to better understand the invention and its implementation inpractice, a plurality of embodiments will now be described, by way ofnon-limiting example only, with reference to the accompanying drawings,wherein

FIG. 1, illustrates (see upper figure) a schematic cross section (sideview) of an MRI device (110) having an open bore with a volume ofinterest (103), where maximal magnetic field is applied and an MSM (200)adjacent to the aperture of the bore; lower curve shows the strength ofthe magnetic field as a function of the distance between the center ofthe VOI (103, where maximal magnetic field is applied, 104) and atheoretical line provided throughout bore's opening (102, where a muchless infringing magnetic field, namely, the magnetic field outside themagnet itself, is applied, 105), and the outer environment surroundingthe MRD (106, where zero magnetic field is applied, 107);

FIG. 2A to 2F, illustrate schematic front views of a few MSMs accordingto several embodiments of the invention;

FIGS. 3 and 4 illustrate schematic perspective views of otherembodiments of the invention; MRD (110) in connection with a gantry(300) where patients (1) are placed before their imaging within the MRD;an MSM (200) is in connection with the gantry;

FIG. 5 illustrates gate (400) to an MRD (110) and/or MRD's cabinet, thegate is in connection with an MSM (200); and

FIG. 6A illustrates MRD (101) which is in connection with a portable orotherwise moveable MSM that can be configured in more than onepredefined location while FIG. 6B illustrates the strength of themagnetic field as a function of the distance between the center of theVOI.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The following description is provided, alongside all chapters of thepresent invention, so as to enable any person skilled in the art to makeuse of the invention and sets forth the best modes contemplated by theinventor of carrying out this invention. Various modifications, however,will remain apparent to those skilled in the art, since the genericprinciples of the present invention have been defined specifically toprovide a means and method for avoiding penetration of metallic objectsthroughout an aperture, towards the open bore of an MRI device.

The term “metallic objects” refers hereinafter to any metal thatproduces a magnetic field in response to an applied magnetic field suchas ferromagnetic and ferrimagnetic metals.

Reference is made now to FIG. 1, illustrating (see upper figure) aschematic cross section (side view) of an MRI device (110) having anopen bore with a volume of interest (103) where maximal magnetic fieldis applied. The bore has an aperture (102), via which the patient isexamined. FIG. 1, further illustrates (see lower curve) the strength ofthe magnetic field as a function of the distance between the center ofthe VOI (103, where maximal magnetic field is applied, 104) and atheoretical line provided throughout bore's opening (102, where a muchless infringing magnetic field, namely, the magnetic field outside themagnet itself, is applied, 105), and the outer environment surroundingthe MRD (106, where zero magnetic field is applied, 107). FIG. 1 furtherillustrates, according to one embodiment of the invention, a ring-shapedmagnetic shielding member (MSM, 200) located in at the outside portionof the MRD, adjacent to the rim of the bore's opening (102). Themagnetic strength of MSM (101, see lower curve) is effectively higherthan the fringing magnetic fields (ibid., 105) of the MRD. Metallicinstruments accidently provided adjacent the opening 102 will thusmagnetically be pulled in a safe manner towards MSM 200 rather thanmagnetically attracted to penetrate aperture 102 towards the MRD'smagnet located within the open bore.

Reference is still made to FIG. 1, showing an example of the invention:The magnetic shielding mechanism (MSM, 200) is especially adapted foravoiding dangerous penetration of metallic objects such a surgicaltools, medical devices and sharp instruments throughout an aperture(102), towards the open bore of an MRI device (MRD, 110), where (103)the magnetic field (B, 104) is maximized. The MRD comprises fringingmagnetic field (B_(P/L), 105) which decreases with increasing distance(L, x-axis of the curve) from aperture (102). MSM (200) comprises atleast one magnet with a magnetic field B_(MSM) (101). The MSM is affixedat a distance L_(MSM) from said MRD's VOI, outside the MED; here forexample, the distance between the aperture and the MSM is approximatelyzero; wherein at any distance L, B_(MSM)>>B_(F/L).

Reference is made now to FIG. 2A to 2F, illustrating schematic frontviews of some of the embodiments of the invention. FIG. 2A presents oneconfiguration of MSM (200) comprising as an example an upper magnet 201and/or a lower magnet 202. FIG. 2B presents another configuration of MSM(200) comprising a plurality of magnets (201, 202 etc). FIG. 2B presentsanother configuration of MSM (200), comprising one or more continuousshaped magnets (201). FIG. 2B presents another configuration of MSM(200), namely a gate-like MSM comprising one or more magnets (201, 202)located outside the bore's aperture (102). FIG. 2E and FIG. 2F present,still in a non limiting manner, other configurations of MSM (200), here,a ring-like MSM is provided above or at least partially around an MRD'sgantry, horizontal patient bed and the like (300).

Reference is made now to FIG. 3, illustrating a schematic perspectiveview of another embodiment of the invention. MRD (110) in connectionwith a gantry (300) where patients (1) are placed before their imagingwithin the MRD. According to this embodiment of the invention, an MSM(200), is in connection with said gantry, e.g., positioned opposite tothe MRD's aperture (102). The magnetic strength of the MSM iseffectively stronger (101) than the fringing magnetic field at itslocation (107) and significantly weaker than the magnetic field appliedin the VOI (104). Moreover, the magnetic field curve of the MSM (101) isvery sharp. Top view of the magnetic gantry (300) is given at view 300A.

Reference is made now to FIG. 4, illustrating a schematic perspectiveview of another embodiment of the invention. An MRD (110) in connectionwith a gantry (300) of another type. According to this embodiment of theinvention, as described above, MSM (200) is in connection with saidgantry, e.g., positioned in opposite to the MRD's aperture (102). Asshown separately in a top schematic view, gantry 300D comprises amagnetic rim (300B) at the circumference of a non-magnetic portion ofthe gantry (300C). The magnetic strength of the MSM is effectivelystronger (101) than the fringing magnetic field at its location(105-107) and significantly weaker than the magnetic field applied inthe VOI (104). The magnetic field curve of the MSM (101) has a broadshape.

Reference is made now to FIG. 5, illustrating a schematic perspectiveview of another embodiment of the invention. A gate (400) to an MRD(110) and/or MRD's cabinet is in connection with an MSM (200). Patientto be imaged is guided to pass said MSM before approaching the MRD'sadjacent environment. The magnetic field (101) within gate (400) issignificantly greater than the magnetic fringing field (107) at thatlocation.

Reference is made now to FIG. 6A, illustrating a schematic perspectiveview of another embodiment of the invention. MRD (101) is in connectionwith a portable or otherwise moveable MSM, which can be configured inmore than one predefined location. In one example of the invention, MSMis situated close to MED's bore opening (e.g., at the bore's aperture orin adjacent to the aperture) at location 200A, along the MRD's gantry(300) at location 200 b or at respectively remote location 200 c, neargantry's end. In one embodiment of the invention, MSM is reversiblyreciprocated by means of telescopic mechanical mechanism, by one or morelevers or transformation means or in any other useful mechanism. FIG. 6Billustrates the strength of the magnetic field as a function of thedistance between the center of the VOI.

1. A magnetic shielding mechanism (MSM) for avoiding penetration ofmetallic objects throughout an aperture, towards the open bore of an MRIdevice (MRD), where the magnetic field (B) is maximized; said MRDproduces fringing magnetic field (B_(F/L)) which decreases withincreasing distance (L) from said aperture; said MSM comprising at leastone magnet with a magnetic field B_(MSM); said MSM is affixed at adistance L_(MSM) from said MRD's aperture; wherein at any distance L,B_(MSM)>>B_(F/L).
 2. The MSM of claim 1, wherein said MSM is configuredas a rim, at least partially encircling said open bore.
 3. The MSM ofclaim 1, wherein said MSM comprises an array of a plurality of magnetsdisposed along at least a part of the circumference of said rim.
 4. TheMSM of claim 1, wherein said MSM is in connection with a gantry asconfigured to reversibly and reciprocally maneuver into and out of saidopen bore, along the main longitudinal axis of same, wherein said MSM isadapted to one of a group consisting of (i) encircle at least a portionof said gantry, (ii) located in connection to said gantry, (iii) becomprised within or on top at least a portion of said gantry and acombination thereof.
 5. The MRD of claim 2, wherein said MSM comprises aplurality of magnets.
 6. The MSM of claim 1, wherein said plurality ofmagnets are provided in an array.
 7. The MSM of claim 1, wherein saidmetallic objects are selected from a group consisting of medicaldevices, needles and surgical instruments, laboratory items, dress-ware,garments, and foot-ware, ferrous-based materials, nickel alloys andstainless steel of ferritic and martensitic crystalline structure andany combination thereof.
 8. The MSM of claim 1, comprising communicationmeans thereby providing a remote connection with an MRD.
 9. The MSM ofclaim 1, wherein said MSM is in connection with an alarming mechanism incommunication with at least one MSM, and further wherein at least oneMSM is provided in connection to a gate alarming when metallicinstrument penetrate via said gate.
 10. The MSM of claim 1, wherein saidMSM is in connection with an MRD-guard mechanism (GM), said GM isselected from a group consisting of (i) MRD's aperture-blockingmechanism, (ii) magnetic field shutter, (iii) one or more MSMs, and acombination thereof, wherein said alarming mechanism in communicationwith said GM when a metallic instrument penetrate via said gate.
 11. TheMSM of claim 1, wherein said MSM is in communication with a metaldetector.
 12. The MSM of claim 1, wherein said MSM is portable.
 13. Amagnetic resonance device (MRD), comprising one or more magneticshielding mechanisms (MSMs) for avoiding penetration of metallic objectsthroughout an aperture, towards the open bore of said MRD where themagnetic field (B) is maximized; said MRD produces fringing magneticfield (B_(F/L)) which decreases with increasing distance (L) from saidaperture; wherein said MSM comprising at least one magnet with amagnetic field B_(MSM); wherein said MSM is affixed at a distanceL_(MSM) from said MRD's aperture; and further wherein at any distance L,B_(MSM)>>B_(F/L).
 14. The MRD of claim 13, wherein said MSM isconfigured as a rim, at least partially encircling said open bore. 15.The MRD of claim 13, wherein said MSM comprises an array of a pluralityof magnets disposed along at least a part of the circumference of saidrim.
 16. The MRD of claim 13, additionally comprising a gantryconfigured to reversibly reciprocally maneuver into and out of said openbore, along the main longitudinal axis of the same, wherein said MSM isadapted to one of a group consisting of (i) encircle at least a portionof said gantry, (ii) located in connection to said gantry, (iii) becomprised within or on top at least a portion of said gantry and acombination thereof.
 17. The MRD of claim 13, wherein said MSM comprisesa plurality of magnets.
 18. The MRD of claim 17, wherein said pluralityof magnets are provided in an array.
 19. The MRD of claim 13, whereinsaid metallic objects are selected from a group consisting of medicaldevices, needles and surgical instruments, laboratory items, dress-ware,garments, and foot-ware, ferrous-based materials, nickel alloys andstainless steel of ferritic and martensitic crystalline structure andany combination thereof.
 20. An MRD system, wherein said MRD is in aremote connection with an MSM as defined in claim
 1. 21. The MRD systemof claim 20, comprising an alarming mechanism in communication with atleast one MSM, wherein at least one MSM is provided in connection to agate alarming when metallic instrument penetrate via said gate.
 22. TheMRD system of claim 21, further comprising an MRD-guard mechanism (GM),said GM is selected from a group consisting of (i) MRD'saperture-blocking mechanism, (ii) magnetic field shutter, (iii) one ormore MSMs, and a combination thereof, wherein said alarming mechanism incommunication with said GM when a metallic instrument penetrate via saidgate.
 23. The MRD of claim 13, wherein said MSM is in communication witha metal detector.
 24. The MRD of claim 13, wherein said MSM is portable.